1. Field of the Invention
The present invention relates generally to electric motors and, more particularly, to electric motors comprising permanent magnets. Specifically, one example in accordance with the present invention provides a compact high-efficiency motor comprising at least two sets of permanent magnets and further comprising electromagnets incorporated to be energized by a control system to provide a variable-speed motor that produces high torque and a method for providing a compact high-efficiency, variable-speed permanent magnet motor that produces high torque.
2. Description of the Prior Art
Known electric motors employ an electrical current to generate a magnetic field that interacts with another magnetic field to induce motion. There are two physical components for all electric motors, the armature, or rotor, which moves and the stator which is stationary. Known technologies for electric motors generally fall into two categories, fully-powered and a powered/passive combination. For a fully-powered motor an electrical current is used to generate the magnetic fields for both the rotor and stator. A combination motor incorporates permanent magnets to supply one of the magnetic fields, and an electrical current generates the other. Combination motors are typically operated from a DC power source.
An electric/magnetic motor operates by utilizing the magnetic attraction/repulsion between magnetic fields that are from the rotor and stator. When these two fields are directly opposite from each other, and magnetically centered, there is a maximum attraction between the two fields, but no torque is being applied to the rotor. To induce motion/torque into the rotor, the magnetic centers must be offset from each other to induce torque on the rotor.
U.S. Pat. No. 8,089,187, the disclosure of which is hereby incorporated by this reference in its entirety, describes a combination motor that includes two sets of permanent magnets and further includes electromagnets incorporated to be energized by a control system to provide a high-efficiency, variable-speed motor that produces high torque. In a described example, there are arrays of permanent magnets that are arranged as described, comprising two rows of permanent magnets wherein one row is mounted on a rotational magnetics assembly and another row of permanent magnets is mounted on a stationary magnetics and electromagnetics assembly. Although having the advantages of providing a high-efficiency, variable-speed motor that produces high torque that facilitates construction, the motor described in U.S. Pat. No. 8,089,187 may nevertheless have a size that is not compatible with all applications for such a motor.
It would be desirable to provide a motor that accommodates the size limitations of applications for motors that comprise two sets of permanent magnets. More particularly, it would be desirable to provide a motor that can be controlled to provide high torque at variable speed with high efficiency that is compact and may therefore be utilized for applications in which size imposes a constraint.